diff --git a/planning/models/planning.py b/planning/models/planning.py
index 6769cad..f590aa0 100755
--- a/planning/models/planning.py
+++ b/planning/models/planning.py
@@ -10,7 +10,7 @@ import uuid
 from math import ceil
 
 from odoo import api, fields, models, _
-from odoo.exceptions import UserError, AccessError
+from odoo.exceptions import UserError, AccessError, ValidationError
 from odoo.osv import expression
 from odoo.tools.safe_eval import safe_eval
 from odoo.tools import format_time
@@ -92,6 +92,25 @@ class Planning(models.Model):
         ('check_allocated_hours_positive', 'CHECK(allocated_hours >= 0)', 'You cannot have negative shift'),
     ]
 
+    @api.constrains('start_datetime', 'end_datetime', 'employee_id')
+    def _check_same_time_valid(self):
+        if self.ids:
+            self.flush(['start_datetime', 'end_datetime', 'employee_id'])
+            query = """
+                SELECT S1.id,count(*) FROM
+                    planning_slot S1, planning_slot S2
+                WHERE
+                    S1.start_datetime < S2.end_datetime and S1.end_datetime > S2.start_datetime and S1.id <> S2.id and S1.employee_id = S2.employee_id
+                GROUP BY S1.id;
+            """
+            self.env.cr.execute(query, (tuple(self.ids),))
+            overlap_mapping = dict(self.env.cr.fetchall())
+            for slot in self:
+                if overlap_mapping.get(slot.id, 0) >= 1:
+                    raise ValidationError(_('Planning already assigned for this employee at the same time.'))
+
+
+
     @api.depends('employee_id')
     def _compute_planning_slot_company_id(self):
         if self.employee_id: